In machine translation, a parallel translation dictionary is searched with respect to an input word input in a first language, and a translated sentence of a second language is output. For example, when a plurality of candidates exist as a translated sentence of the second language, information on a second language side is utilized, and an adequate translated sentence is selected.
Related techniques are disclosed in Japanese Laid-open Patent Publication No. 5-298359, Japanese Laid-open Patent Publication No. 4-372061, and Japanese Laid-open Patent Publication No. 2008-269413.